The invention relates to covers for application to open load beds of light trucks and, more particularly, to an improved cover design having a lift-roof providing improved access to the load bed and extending vehicle functions to additional uses.
Reference is made here to U.S. Pat. No. 4,533,171 (Lake) for an improved Lift-Roof Trailer. The invention seeks to satisfy a demand for benefits similar to those provided by the referent lift-roof trailer, but as applied to light open bed trucks, and has been pursued in response to need expressed by owners of such vehicles who participated in market surveys for the improved lift-roof trailer at the Detroit Camper and Travel Trailer Show of 1983 and the MUCC Outdoorama Show of 1984 in Detroit.
Various forms of fixed cover have been manufactured for use with open load bed light trucks. These prior art forms include covers fabricated primarily from fiberglass reinforced plastic or from aluminum. In the majority of designs, these covers present a front view profile which is approximately matched with the front view profile of the passenger compartment or cab, so that maximal volume enclosure is provided relative to the vehicle frontal area and, hence, maximal load volume efficiency relative to fuel economy. The majority of these covers of the prior art are also fixedly attached to the load bed on which they are mounted, except at the rear wall area above the vehicle load bed tailgate. The rear wall usually incorporates an approximately vertical access door, or window, attached at its upper edge to the main structure of the cover by lateral hinging means and equipped with latching and locking means to provide security when closed. Such designs of fixed mount, cab height cover are hereinafter referred to as conventional fixed mount covers.
Primary objectives of load bed cover designs for light trucks include to provide secure, fully enclosed protection for a maximal load volume, within capacity constraints for the vehicle and its load bed. Secondary objectives include the provision of convenient access to the cargo area and optimization of vehicle fuel economy and dynamic handling effects due to aerodynamic and weight characteristics of the cover within the constraints of other objectives. However, to some degree, when a fixed mount design is used, a conflict exists between the need for optimal fuel economy with acceptable vehicle handling and the desire for convenient access. This is because any increase in cover height above the passenger cab roof will increase the frontal area, thereby reducing fuel economy due to an associated increase in vehicle aerodynamic drag, as well as possibly adversely affecting vehicle handling due to a raised center of gravity. Therefore, most covers incorporate a roof surface which is aerodynamically blended with that of the passenger cab. With existing conventional fixed mount designs of the prior art, although volume enclosure is near maximal relative to any vehicle fuel economy effects, access is limited to rear entry and this is via an opening which is limited, with respect to fuel economy, by the height of the vehicle passenger cab. This access may be improved with use a sloping rear door or window and by raising the roof height toward the rear of the cover. However, such designs may compromise fuel economy and/or load volume capacity for a small improvement in access from the rear, with little or no improvement in access from the sides.
Various other types of cover have been marketed which have been designed to provide improved levels of convenience in access to the load bed, while also providing secure load enclosure when required. These include rigid covers having a frontal profile of lower than cab height, which are pivoted about a lateral axis in proximity to the upper edge of the load bed forward wall. With such forward-hinged rigid covers, a low profile has been found necessary to maintain an acceptable appearance with a shape which avoids interference of the cover with the passenger cab, when in an open position. A load bed cover of this concept has been marketed by J. K. Enterprises of Pacific Grove, Calif. Another low profile cover concept providing improved access from above the load bed employs two roof sections with opening accomodated by the sliding action of one section above or below the other, as in a cover marketed by Robbins Products of Arlington, Tex.
A major disadvantage of low profile covers is that a significant portion of the enclosed load volume is given up relative to that provided by a conventional cover of full cab height. This disadvantage is avoided, in a two section sliding cover marketed by Specialty Equipment Sales of West Bend, Ind. by adding walls to extend the cover to full cab height. However, the complexity and cost of manufacture become less competitive.
Other lift-roof cover designs have employed a lateral pivot axis at a cover forward roof surface in a location somewhat rearward of the forward wall, so that a rearward portion may be pivoted upward for improved access. Such designs have generally been pursued in fiberglass reinforced plastic, but have resulted manufacturing costs which are relatively high with volume capacity and access which are less than may be desirable.
A lower cost method, which has been employed to provide access from the side with full volume enclosure, has used a conventional cover form with a longitudinal pivot axis on one side of the vehicle. However, while access from one side is improved with an open cover, access from the rear and from the other side is still relatively restricted. A load bed cover marketed by Keil Manufacturing, Inc. of Napoleon, Mich. overcomes this deficiency by employing a flexible, weatherproof fabric stretched over rigid, but movable, rigid support hoops of cab height. In this concept, the rigid support hoops may be slid forward on rails which are fixedly mounted to the upper edges of the two load bed side walls, and so provide the desired improved access to the load bed. However, this concept has obvious limitations in the levels of security provided and introduces new complexities in methods of manufacture and installation relative to conventional fixed mount covers of full cab height.
Since the majority of light truck load bed covers are of conventional, full cab height, fixed mount design, the methods for manufacturing and distribution of load bed covers have been developed, in the majority, to suit these conventional designs. Any design of load bed cover which cannot be manufactured, handled or stored using the methods and equipment established for conventional covers is, therefore, likely to involve additional costs in bringing it to the user.